Combining algae cultivation and co2 capture

Abstract

The invention relates to the field of culturing algae and use of algae-derived products. The invention also relates to the reduction of CO 2 emission. More in particular the invention relates to combining the capture and conversion of CO 2 from flue gas or biogas and the growth of algae. The invention provides a method for advantageously combining reduction of CO 2 emission with algal growth.

1 . A method of promoting growth of algae using an absorbent liquid comprising carbon dioxide, the method including the steps of:
 (1) contacting a gas comprising carbon dioxide with an absorbent liquid,   (2) allowing the absorbent liquid to absorb carbon dioxide from the gas,   (3) contacting the absorbent liquid comprising the absorbed carbon dioxide to with an algal culture, and   (4) allowing the algal culture to convert the carbon dioxide from the absorbent liquid, thereby regenerating the absorbent liquid and promoting the growth of algae in said algal culture.   
     
     
         2 . A method according to  claim 1 , wherein
 in step (1), a gaseous stream comprising carbon dioxide is contacted with a liquid stream of absorbent liquid, and   in step (3), the liquid stream is added continuously to the algal culture,   the method further comprising the step of:
 (5) recycling the regenerated absorbent liquid to be contacted with the gaseous stream in method step (1). 
   
     
     
         3 . A method according to  claim 1 , wherein steps (1), (2) and (3) are performed simultaneously. 
     
     
         4 . A method according to  claim 1 , wherein
 in step (1), a fixed amount of carbon dioxide is first added to a batch reactor containing a fixed amount of an absorbent liquid, and   in step (2), the fixed amount of absorbent liquid is allowed to absorb the carbon dioxide for a fixed period of time before in step (3), said absorbent liquid is contacted with the algal culture.   
     
     
         5 . A method according to  claim 3 , wherein
 a fixed amount of carbon dioxide is added to a batch reactor containing a fixed amount of absorbent liquid, growth medium and algae, and   the carbon dioxide is allowed for a fixed period of time to be absorbed by the absorbent liquid and be converted by the algae, before harvesting said algae.   
     
     
         6 . A method according to  claim 1 , wherein
 the carbon dioxide captured in the absorbent liquid is   a) carbon dioxide from flue gas, comprising 5-25% carbon dioxide, balanced mainly by nitrogen (70-90%) at atmospheric conditions, or   b) is carbon dioxide from biogas comprising 20-50% carbon dioxide, balanced by mainly methane (45-75%) at a pressure of between 1-20 bar.   
     
     
         7 . A method according to  claim 1 , wherein said absorbent liquid is first added to an aqueous solution used for culturing algae, before said absorbent liquid is added to the algal culture. 
     
     
         8 . A method according to  claim 1 , wherein said algae tolerate a pH of above 8.0. 
     
     
         9 . A method according to  claim 1 , wherein said absorbent liquid has a pH of above 8.0. 
     
     
         10 . A method according to  claim 8 , wherein said aqueous solution, used for culturing algae, has a pH of above 8.0. 
     
     
         11 . A method according to  claim 1 , wherein said algal culture comprises  Spirulina platensis, Neochloris oleoabunduns, Chlorella vulgaris , or  Scenedesmus obliquus.   
     
     
         12 . A method according to  claim 1 , the method further comprising the steps of:
 harvesting said algae from said algal culture, and   extracting one or more bio-fuel precursors and/or one or more chemical species, selected from the group consisting of amino acids, vitamins (such as β-carotene, vitamin B 1 , B 6 , B 12 , E, K 1 , and K 2 ), minerals, and nutritional and pigment-like compounds, such as polysaccharides, phycocyanin, and chlorophyll, from said algae the method optionally further comprising:   preparing bio-fuel from said bio-fuel precursors.   
     
     
         13 . A method according to  claim 1 , wherein said absorption liquid comprises an amino acid, one or more selected from the group consisting of β-alanine, sarcosine, 6-amino-hexanoic acid, taurine and L-glutamic acid, an amine, one or more selected from the group consisting of monoethanolamine and methyl diethanolamine, or carbonates, one or more selected from the group consisting of K 2 CO 3 , Na 2 CO 3 , and NH 4 HCO 3 . 
     
     
         14 . A method according to  claim 1 , wherein said absorbent liquid comprises taurine. 
     
     
         15 . A composition comprising a mixture of an algal culture medium and an absorbent liquid, wherein the composition comprises about one part standard algal culture medium mixed with one part absorbent liquid. 
     
     
         16 . A composition according to  claim 15 , wherein said absorbent liquid comprises taurine. 
     
     
         17 . A composition according to  claim 15 , wherein the composition comprises algal nutrients like nitrogen (N), phosphorus (P), and potassium (K), silica, iron, ethylenediaminetetraacetic, and micro-nutrients like trace elements, trace metals, minerals, and vitamins. 
     
     
         18 . A method according to  claim 6 , wherein
 the carbon dioxide captured in the absorbent liquid is carbon dioxide from biogas, comprising 20-50% carbon dioxide, balanced by mainly methane (45-75%) at a pressure of between 1-20 bar.   
     
     
         19 . A method according to  claim 12 , the method further comprising the step of preparing bio-fuel from said bio-fuel precursors. 
     
     
         20 . A method according to  claim 13 , wherein the amino acid is selected from the group consisting of β-alanine, sarcosine, 6-amino-hexanoic acid, taurine and L-glutamic acid; the amine is selected from the group consisting of monoethanolamine and methyl diethanolamine; and the carbonates are selected from the group consisting of K 2 CO 3 , Na 2 CO 3 , and NH 4 HCO 3 .